This invention relates to circuit breakers. More particularly, it is concerned with low voltage circuit breakers for controlling low and moderate power electrical circuits. Thus, it is an object of this invention to provide new and improved circuit breakers of such character.
A circuit breaker for use in controlling electrical circuits typically has a set of contacts, one fixed and one moving, and a toggle, or overcenter mechanism, which is manually operated to close and open the contacts. A circuit breaker also includes an overload mechanism for tripping the circuit breaker and opening the contacts when the electrical current through the circuit breaker exceeds certain predetermined conditions. The overload mechanism may include a thermally responsive member such as a thermostat element which functions to trip the breaker when an overload current exists. The circuit breaker may also include a magnet and armature arrangement for tripping the breaker rapidly in response to certain predetermined conditions.
A variety of circuit breakers of the general form described above are well-known and widely used. One particularly useful type of circuit breaker employed in protecting low voltage low and moderate power circuits is described and claimed in U.S. Pat. No. 3,671,908 issued on June 20, 1972 to Harold E. Belttary and John G. Palmer entitled "Circuit Breaker". Circuit breakers as described in the aforementioned patent are completely satisfactory for use in their intended applications. However, for certain applications it is desirable to provide a circuit breaker in which the number and complexity of parts are reduced, thereby also reducing the costs of fabrication and assembly. A circuit breaker of simplified construction is described and claimed in U.S. Pat. No. 3,904,998 issued Sept. 9, 1975 to Harold E. Belttary entitled "Circuit Breaker".
In certain applications, it is desirable to employ two or more circuit breakers in combination so that when any one is tripped in response to an overload condition the others will be tripped also. Typically, the circuit breakers are mounted in side-by-side relation with an interconnection between the tripping mechanisms. Circuit breakers as described in the foregoing patent employ a simplified triggering arrangement and are not readily adapted for interconnection so as to cause mutual tripping.
In other applications, it is desirable to provide the magnet and armature arrangement for rapidly tripping a breaker to an existing mechanism which does not provide magnetic sensing, such as, for example, the mechanism disclosed in U.S. Pat. No. 3,909,764 issued on Sept. 30, 1975 to Harold E. Belttary entitled "Electric Circuit Breaker". Thus, it is another object of this invention to provide new and improved arrangements of such character.
Many inexpensive magnetic systems employed in circuit breakers are not independent of thermal calibration in that thermal calibration may change the gap between armature and pole faces or may have an effect on latch loading. Hence, it is an object of this invention to provide for new and improved circuit breakers in which the sensitivity of the "Magnetic Trip Level" is independent of "Thermal Calibration" settings.